WATER: Monday morning bleaching and post-vacation blues

When Joy Boutrup and I were teaching at Penland earlier in the summer she told the story of “Monday morning bleaching”. In old European laundries there was a serious problem with an increased number of holes left in fabrics that were laundered on Monday mornings. During the rest of the week the problem was lessened.


The issue turned out to be iron pipes. Water that had been sitting in the pipes all weekend leached ferrous out of the metal pipes. When ferrous is combined with bleach, the fabric will be compromised, resulting in holes. Once enough water had flowed through the pipes the amount of ferrous was decreased and there was no problem the rest of the week.

I have just experienced a related phenomenon in my own dye studio. After being away from home and studio a week or more, I observed that the water coming out of the studio tap was dark in color. Did this have to do with our shallow well? Was there contamination?

I suspected iron and tested the water for ferrous by stirring a very small amount of gall nut tannin into the water. When ferrous and tannin combine, the water will turn black. This is the principle of gall nut ink, which is made from iron + gall.

A small amount of gall nut tannin was added to both cold and hot water

Water from the studio cold tap was fine. There was no reaction whatsoever. But the hot water turned black immediately, indicating that there was likely a problem with my “on demand” hot water heater. A call to the plumber confirmed that after 10 years of use the heating element had likely deteriorated and the water was leaching iron from the housing of the tank.


I continued to observe the water. After running the tap regularly for two days the iron content was much less but still too dark to be acceptable for dyeing.

After 5 days the hot water seemed to be almost completely clear of ferrous – but not quite.


This was not a good situation for a dye studio and I was forced to use only water from the cold tap for all processes. Yesterday I had a new water heater installed. All water is now completely free of ferrous!

IMG_8927 (1)

Soft acidic water is far more likely to dissolve iron in pipes or other sources. Hard, alkaline water won’t present as much of a problem. My mountain well water is very soft and close to pH 6, which is slightly acidic – the perfect water to leach any metal available. It’s a reminder that all dyeing begins with the water. Some mysteries in the dye studio can be solved by simply looking at the water.




12 thoughts on “WATER: Monday morning bleaching and post-vacation blues

  1. Found your water issue and observations fascinating. There are so many variables to consider when faced with a problem like this. Glad you solved this.

  2. thnk u so much for your guidance ! & very interesting data on natural dyeing technology ! its true i had also so many worked on it , getting same problem about that .thank so much ones again..
    i m ask one question for u .pls send me any idea for natural dyeing effluent water treatment plan.
    i hav it . & how to treat the weast water for natural dyeing. pls guide me .

    1. Maruti,
      These are good questions but they are also big and complex ones. I don’t feel that I have the ability to answer them adequately within the scope of the blog. My own studio practice is relatively small.
      Do keep in mind that all dyeing is dependent on good mordanting and choice of dyes. If the mordant does not attach to the fiber, then the dye won’t either. Sappanwood is not considered a very lightfast dye.
      As far as disposal, it’s best to recycle as much as possible (mordant or tannin baths) and throw out very little. Most things coming out of my own studio can be added to the compost or the waste water system without concern, though it is best to neutralize anything that is highly acidic or alkaline first.

  3. this is thought provoking for me as my new home’s water source has some problems…thanks for the leg up to how to think about solving this.

  4. I live in northern Minnesota where shallow wells are very high in ferrous. I have a very deep well now, with no issues, but it used to be depressing to make a cup of tea and have it go black. Back then I did not realize it was probably the tannin making that “sad” thing happen…Vernal

  5. thank you for posting… an important lesson to tuck away in my knowledge base…. I do have 2 questions… do you know the composition/ph of rain water? and where do you get the gall nuts? Thanks!

  6. Timely post with this drought we’re having in Ontario! This summer I am trying the urine-indigo vat on wool and enjoying the results. I am hoping to visit you one day, or are you teaching in these parts any time soon? Wishing to travel to Oaxaca for ISS10…..

  7. Catherine, this is very interesting. I am fascinated with the whole issue of water and water source. Right now I am running samples with distilled, brook, well (usually hard around here) and spring (usually soft) to see the differences. I suspect, especially with dyes like cochineal and madder, that the type of water to get best color will be different. My well water produces that good red in madder that I must add chalk to in softer water or public water sources. I use distilled for a control but of course buying water is not sustainable or in any way practical for larger scale dyeing. But when teaching I sometimes have to resort to it. Thanks!

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